Milk thistle has been used medicinally for over 2,000 years, most commonly for the treatment of liver and gallbladder disorders. Silymarin comes from the seeds of milk thistle and is believed to be the active part of milk thistle. The terms "milk thistle" and "silymarin" are often used interchangeably.

Milk thistle products are popular in Europe and the United States for various types of liver disease. Although numerous human trials have been published, most studies have lacked a strong design and strong conclusive evidence.

Milk thistle has been well tolerated with mild side effects when used in a recommended amount and duration.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

GRADE *

Multiple studies from Europe suggest benefits of oral milk thistle for cirrhosis. In studies up to five years long, milk thistle slightly improved liver function and decreased the number of deaths in people with liver disease. Although these results are promising, most studies have been poorly designed. Better research is necessary before a strong conclusion can be made.

B

Research showed that milk thistle improved control of blood sugar in people with diabetes with and without liver disease. Higher quality research is necessary before strong conclusions can be made.

B

Research suggests that silymarin improves blood and urine markers associated with diabetic kidney disease. Further high quality research is needed before a conclusion can be made.

B

Several studies of milk thistle in liver disease caused by viruses or alcohol report improvements in liver tests. However, most studies have been small and poorly designed. More research is needed before a conclusion can be made.

B

Existing research shows unclear benefits for the use of milk thistle in acute viral hepatitis, or liver inflammation due to an infection from a virus. Further research is needed to draw conclusions.

C

Limited research showed that milk thistle reduced the severity of allergic nasal symptoms. Further study is needed to draw conclusions.

C

Milk thistle has been used traditionally to treat Amanita phalloides mushroom poisoning. Strong research in humans supporting this use is lacking. Further research is necessary.

C

Early research suggests that milk thistle, alone or given with vitamin E, improves antioxidant status. Although promising, further high quality research is needed before conclusions can be made.

C

Early evidence reported unclear results for the use of milk thistle in combination with other supplements in people with cancer. One person reported an improvement in liver cancer after taking milk thistle. Further research is needed to draw conclusions.

C

In women undergoing artificial fertilization (in vitro fertilization, IVF), silymarin used in combination with standard therapy has demonstrated mixed results. More research is needed to reach conclusions.

C

An herbal preparation containing milk thistle may be effective in decreasing heartburn. Research of milk thistle alone is necessary for conclusions to be drawn.

C

Although non-human research suggests cholesterol-lowering effects of milk thistle, human studies have provided mixed results. Further studies are necessary before a firm conclusion can be made.

C

Several studies suggest possible benefits of milk thistle to treat or prevent liver damage caused by drugs or toxic chemicals. Results of this research are unclear, and most studies have been poorly designed. Higher quality trials are necessary to draw conclusions.

C

An herbal preparation containing milk thistle may be effective in decreasing menopausal symptoms. Research of milk thistle alone is necessary for conclusions to be drawn.

C

In early research, a preparation of milk thistle and other supplements has demonstrated a beneficial effect on people with various neurodegenerative disorders, including multiple sclerosis (MS), Parkinson's disease, and Alzheimer's disease. Further high-quality research with milk thistle alone is needed before any firm conclusions can be made.

C

In human research, milk thistle reduced symptoms of obsessive compulsive disorder (OCD), but lacked benefits compared to regular treatment. Further research is needed to draw conclusions on the benefits of milk thistle in OCD patients.

C

Early evidence suggests that milk thistle has anti-inflammatory effects in people with osteoarthritis. Further high quality research is needed before conclusions can be made.

C

Early research in breast cancer patients suggests that silymarin (Levidaerm®) helps ease radiotherapy-induced toxic skin reactions compared to standard care. Further high quality research is warranted.

C

Human research showed that adding milk thistle to regular therapy lacked further benefits for iron overload in people with beta-thalassemia. Further study is needed before firm conclusions may be made.

F

* Key to grades

A: Strong scientific evidence for this useB: Good scientific evidence for this useC: Unclear scientific evidence for this useD: Fair scientific evidence for this use (it may not work)F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

For acute viral hepatitis, 160-800 milligrams of silymarin (e.g. Legalon®) has been taken by mouth daily in three divided doses for three weeks.

For allergic nasal symptoms, 140 milligrams of silymarin has been taken by mouth three times daily for one month.

For amanita phalloides mushroom toxicity, silibinin has been taken by mouth; 20-50 milligrams per kilogram of silibinin in 500 milliliters of 5% dextrose solution has been injected into the vein every six hours for one day.

For antioxidant effects, 140 milligrams of silymarin (Livergol®) has been taken by mouth three times daily for three weeks.

For cirrhosis, 160-800 milligrams of silymarin (e.g. Legalon®) has been taken by mouth in 2-3 divided doses daily by mouth for up to two years.

For diabetes (type 2), 200-230 milligrams of silymarin (e.g. Legalon®) has been taken by mouth one to three times daily for four weeks to 12 months, together with regular therapy.

For diabetic nephropathy (kidney disease), 140 milligrams of silymarin has been taken by mouth three times daily for three months.

For liver damage from drugs or toxins, 160-800 milligrams of silymarin (e.g. Legalon®) has been taken by mouth daily in three divided doses for periods ranging from 15 days to five weeks; 70 milligrams of silibinin has been taken by mouth three times daily for 6-12 months.

For fertility, three doses of 70 milligrams of silymarin have been taken by mouth (in addition to standard therapy) over the course of one day.

For high cholesterol, 200-600 milligrams of silymarin has been taken by mouth once or three times daily for four months in addition to standard therapy.

For chronic liver disease 160-480 milligrams of silybin (Silipide®, IdB 1016) has been taken by mouth once or three times daily for up to three months;120-420 milligrams of silymarin (Legalon®) has been taken by mouth daily in three divided doses for four weeks to 12 months; silibinin (e.g. Legalon® SIL) has been injected into the vein for periods of 10-14 days.

For osteoarthritis, 150 milligrams of silymarin has been taken by mouth twice daily for eight weeks.

For radiation skin irritation, a silymarin-based cream (Leviaderm®) has been applied to the skin.

Children (under 18 years old)

For liver damage from drugs or toxins, 80-320 milligrams of silibinin has been taken by mouth daily for 28 days.

Safety
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Avoid in people with known allergy or sensitivity to milk thistle, its parts, or to members of its plant family (e.g. daisies, artichokes, common thistle, and kiwi). Anaphylactic shock (a severe allergic reaction) and rash from milk thistle has been reported in several people.

Side Effects and Warnings

Milk thistle is likely safe when taken in recommended doses for 4-6 years.

Milk thistle is possibly safe when taken in doses greater than recommended, or when taken for more than 4-6 years.

Milk thistle may lower blood sugar levels. Caution is advised in people with diabetes or low blood sugar, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.

Use caution in combination with agents processed by the liver's "cytochrome P450" enzyme system.

Use caution in combination with agents that undergo a chemical process called glucuronidation.

Use cautiously in pregnant or breastfeeding women.

Avoid use of above-ground parts of the milk thistle plant in women with hormone-sensitive conditions, including breast, uterine, and ovarian cancer, endometriosis, and uterine fibroids.

Avoid in people with known allergy or sensitivity to milk thistle, its parts, or to members of its plant family.

Pregnancy and Breastfeeding

Use cautiously in pregnant or breastfeeding women due to a lack of sufficient evidence to support safe use.

Milk thistle has been used historically to improve flow of breast milk, and limited study of milk thistle in pregnant women reported a lack of side effects.

Milk thistle may interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. People using any medications should check the package insert, and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

Milk thistle may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary.

Milk thistle may interfere with the way the body processes certain herbs or supplements using the liver's "cytochrome P450" enzyme system. As a result, the levels of other herbs or supplements may be too high in the blood, and may cause increased effects or potentially serious adverse reactions.

Milk thistle may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.

Milk thistle may also interact with anti-anxiety herbs and supplements, anti-inflammatories, anticancer herbs and supplements, antioxidants, antiretrovirals, antivirals, calcium, cholesterol-lowering herbs and supplements, fertility herbs and supplements, glucuronidated herbs and supplements, herbs and supplements that affect the blood, herbs and supplements that promote milk production, herbs and supplements that affect the liver, herbs and supplements used for the skin, heart, stomach, or intestines, hormonal herbs and supplements, impotence herbs and supplements, iron, N-acetyl cysteine, p-glycoprotein modulators, and vitamin E.

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.